A light emitting diode (LED) is a device including a material emitting light when electrical energy is applied thereto, in which energy generated through electron-hole recombination in semiconductor junction parts is converted into light to be emitted therefrom. LEDs are commonly employed as light sources in illumination devices, display devices, and the like, and thus, the development of LEDs has been accelerated.
In particular, as the development and employment of gallium nitride (GaN)-based LEDs have recently increased, and mobile keypads, turn signal lamps, camera flashes, and the like, using such gallium nitride-based LEDs, have been commercialized, and, in line with this, the development of general illumination devices using LEDs has accelerated. Like the products to which light emitting devices are applied, such as the backlight units of large TVs, the headlamps of vehicles, a general illumination device, and the like, the purposes of light emitting devices are gradually moving toward large-sized products having high outputs and high degrees of efficiency, so a method for enhancing light extraction efficiency of a light emitting device used for the purposes is required.